diff --git a/testcase/src/test/resources/config-localtest.conf b/testcase/src/test/resources/config-localtest.conf
index 22a41d22..222a9d17 100644
--- a/testcase/src/test/resources/config-localtest.conf
+++ b/testcase/src/test/resources/config-localtest.conf
@@ -59,7 +59,7 @@ node.discovery = {
   enable = true
   persist = true
   bind.ip = ""
-  external.ip = null
+  external.ip = ""
 }
 
 node.backup {
diff --git a/testcase/src/test/resources/config-test-dbbackup.conf b/testcase/src/test/resources/config-test-dbbackup.conf
index b39cb54d..830e1184 100644
--- a/testcase/src/test/resources/config-test-dbbackup.conf
+++ b/testcase/src/test/resources/config-test-dbbackup.conf
@@ -62,7 +62,7 @@ node.discovery = {
   enable = true
   persist = true
   bind.ip = ""
-  external.ip = null
+  external.ip = ""
 }
 
 node.backup {
diff --git a/testcase/src/test/resources/config-test-index.conf b/testcase/src/test/resources/config-test-index.conf
index d2feabff..d28f2640 100644
--- a/testcase/src/test/resources/config-test-index.conf
+++ b/testcase/src/test/resources/config-test-index.conf
@@ -55,7 +55,7 @@ node.discovery = {
   enable = true
   persist = true
   bind.ip = ""
-  external.ip = null
+  external.ip = ""
 }
 
 node {